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2017-11-20

ENGINES

  Article  


   
     
 

JET ENGINES  vs  PROPELLERS

 
  Or how to figure out how much thrust a propeller driving engine generates  
     
  See also:  -  -  -  -  -  
     

Formula

--

Example as collected : a 1.5kW engine driving a 0.25m propeller - aircraft speed : 252 km/h

T : engine thrust in Newtons

17.2N (the value looked after) 

Pengine : engine power in Watts 1500W   or 1.5kW  in this example
V : aircraft speed in m/s 70m/s in this example (252 km/h)
n : propeller "efficiency" 80% in this example (excessive)
-      
But since the formula doesn't apply to static thrust or for an aircraft speed = 0(see example below for a 1100kW engine) we have to have to find another approach to the issue, either fix a "theoretical aircraft speed" (then which one...)
T : engine thrust in Newtons

1100000 0.75

1

825000N or

825kN or

185467 lbf

 

which is absurd

Pengine : engine power in Watts 1100000 W
V : aircraft speed in m/s 0 m/s - in practice 1m/s (3.6 km/h)
n : propeller "efficiency" 75%

-

 

Among the aircraft which have been equipped with either a jet or a propeller driving engines, 3 are of particular interest :

P-51D : top speed = 80% of the jet equipped equivalent [F1J-1]
Yak-3 : top speed = 82% of the jet equipped equivalent [Yak15]
J-21B : top speed = 80% of the jet equipped equivalent [J-21R]

Assuming (wrongly) that a 20% less powerful jet engine would then have produced 20% lower top speed, a rule-of-the-thumb approach could be :

F1J-1 : 4000 lbf 80% = 3200 lbf P-51D 1695 hp   1.85 = 3136 lbf   correct appxoximation
Yak15 : 1966 lbf 82% = 1573 lbf Yak-3 1166 hp   1.85 = 2157 lbf   excessive in this particular case
J-21R : 3300 lbf 80% = 2640 lbf J-21B 1457 hp   1.85 = 2729 lbf   correct approximation

Applying this rule-of-thumb to the V610 aircraft, whose cruising speed was about 53% of the V618 jet powered equivalent, we would get:
1630 hp x 1.85 = 3015 lbf or 60.31% of the 5000 lbf engine powering the V618.   Again, not on the mark but not ridiculously wrong....

If "we" have a go at a calculated approach for a static thrust, here what's needed to know about their  engine/propeller associations :

V1650-07 : 1695 hp / 1264 kW driving a 3.35m propeller (11'00" to be exact)
R4360-59 : 3500 hp / 2611 kW driving a 5.05m propeller (16'07" to be exact)
R4370-51 : 4300 hp / 3208 kW driving a 5.05m propeller (16'07" to be exact) + ... 400 lbf of residual thrust

 

Example of aircrafts having been propelled either by a jet or propeller driving engines

Aircraft     Propeller
Engine
Engine
Output
Speed
Cruise
Equivalent
Thrust
Aircraft     Jet
Engine
Engine
Output
Speed
Cruise
P51D30 Mustang 1 V1650-7 1264.kW   380.kn   F1J1 Fury 1 J33-A-2 4000.lbf 475.kn
Yak3 = 1 VK105PF 870.kW   356.kn   Yak15 = 1 RD10 1966.lbf 435.kn
J21B Gam 1 DB605B 1100.kW   346.kn   J21R Gam 1 DGo3 3300.lbf 432.kn
V630 Viscount 4 Dart.502 740.kW   239.kn   V663 Viscount 2 RB44.Tay1 6250.lbf ??
V610 Viking.1B 2 BH.634 1260.kW   182.kn   V618 Viking 2 RB41.Nene 5000.lbf 341.kn
GL41F1a Meteor 2 Trent 559.kW   ??   GL41F1 Meteor 2 Welland 1708.lbf 335.kn
      +thrust 1000.lbf                  
GL41F1b Meteor 2 Trent 350.kW   ??   GL41F1 Meteor 2 Welland 1708.lbf 335.kn
      +thrust 1400.lbf                  
HP56 Provost 1 AL-126 410.kW   174.kn   PH84 Provost 1 BSVp11 2450.lbf 356.kn
___________
 
 
 

Examples of Aircrafts Types Subjected to Propeller and Jet Propulsion

Main source : http://www.aviastar.org/index2.html

Gloster Meteor F1
 MODEL Gloster Meteor F1/Trent
 ENGINE 2 x RR "Trent" turboprops
1305kW / 1750 hp
 ENGINE 2.41m 2 x RR "Trent" turboprops
559kW / 750 hp +
4.45kN / 1000 lbf  / 454kgf
 ENGINE 1.49m 2 x RR "Trent" turboprops
350kW / 1750 hp
6.23kN / 1400 lbf / 635 kgf
 WEIGHTS
    Take-off weight - -
    Empty weight - -
 DIMENSIONS
    Wingspan 13.1 m 43 ft 0 in
    Length 12.6 m 41 ft 4 in
    Height 3.96 m 13 ft 0 in
    Wing area 34.75m 374.05 ft
 PERFORMANCE
    Max. speed === km/h === mph
    Ceiling = m ft
 ARMAMENT 4 x 20mm cannons ???
 MODEL Gloster Meteor F1
 ENGINE 2 x Rolls Royce Welland.I
7.6kN / 1708 lbf
 ENGINE -
-
-
 ENGINE -
-
-
 WEIGHTS
    Take-off weight 6260 kg 13801 lb
    Empty weight 3690 kg 8135 lb
 DIMENSIONS
    Wingspan 13.1 m 43 ft 0 in
    Length 12.6 m 41 ft 4 in
    Height 4.0 m 13 ft 1 in
    Wing area 34.7m 373.51 ft
 PERFORMANCE
    Max. speed 620 km/h 385 mph
    Ceiling 15240 m 50000 ft
 ARMAMENT 4 x 20mm cannons
 
North American P-51D Mustang North American FJ-1 Fury  ("F1J1" in AAC)
 MODEL P-51D Mustang
 ENGINE 1 x Packard V1650-7
1264 kW / 1695 hp
 WEIGHTS
    Take-off weight 5488 kg 12099 lb
    Empty weight 3232 kg 7125 lb
 DIMENSIONS
    Wingspan 11.28 m 37 ft 0 in
    Length   9.83 m 32 ft 3 in
    Height   2.64 m   9 ft 8 in
    Wing area 21.65m 233.04 ft
 PERFORMANCE
    Max. speed 703 km/h 437 mph
    Ceiling 12770 m 41800 ft
 ARMAMENT 6 x 12.7mm MG,
2 x 113kg bomb
 MODEL FJ-1 "Fury"
 ENGINE 1 x Allison J35-A-2 turbojet,
17.8kN / 4000 lbf
 WEIGHTS
    Take-off weight 7076 kg 15600 lb
    Empty weight 4011 kg 8843 lb
 DIMENSIONS
    Wingspan 9.8 m 32 ft 2 in
    Length 10.5 m 34 ft 5 in
    Height 4.5 m 15 ft 9 in
    Wing area 20.5m 220.66 ft
 PERFORMANCE
    Max. speed 880 km/h 547 mph
    Ceiling 9750 m 32000 ft
 ARMAMENT 6 x 12.7mm machine-guns
-
 
Yakovlev Yak-3 Yakovlev Yak-15
Yakovlev Yak-3
 MODEL Yak 3 (1943)
 ENGINE 1 x VK-105PF
870 kW / 1166 hp
 WEIGHTS
    Take-off weight 2650 kg 5842 lb
    Empty weight 2135 kg 4707 lb
 DIMENSIONS
    Wingspan 9.2 m 30 ft 2 in
    Length 8.5 m 28 ft 11 in
    Height 2.4 m 08 ft 10 in
    Wing area 14.8m 159.31 ft
 PERFORMANCE
    Max. speed 660 km/h 410 mph
    Ceiling 10700 m 35100 ft
 ARMAMENT 1 x 20.0mm MG,
2 x 12.7mm MG
 MODEL Yak 15 (1946)
 ENGINE 1 x RD10 turbojet
8.75kN / 1966 lbf
 WEIGHTS
    Take-off weight 2735 kg 6030 lb
    Empty weight 2350 kg 5181 lb
 DIMENSIONS
    Wingspan 9.2 m 30 ft 2 in
    Length 8.7 m 29 ft 7 in
    Height 2.3 m 07 ft 5 in
    Wing area 14.85m 159.84 ft
 PERFORMANCE
    Max. speed 805 km/h 500 mph
    Ceiling 12500 m 41000 ft
 ARMAMENT 2 x 23mm NS-23 cannon
-
 
Hunter Percival P-56 Provost Hunter Percival P-84 Jet Provost
Hunting Percival P.56 Provost
MODEL Hunting Percival P56 (1950)
 ENGINE 1 x 410kW Alvis Leonides 126
410kW / 500 hp
 WEIGHTS
    Take-off weight 1995 kg 4398 lb
    Empty weight 2112 kg 4656 lb
 DIMENSIONS
    Wingspan 10.71 m 35 ft 2 in
    Length 8.73 m 29 ft 8 in
    Height 3.70 m 12 ft 2 in
    Wing area 19.9m 214.20 ft
 PERFORMANCE
    Max. speed 322 km/h 200 mph
    Ceiling 7620 m 25000 ft
 ARMAMENT 2 x machine guns (P56 Mk53)
Hunting Percival P.84 Jet Provost
MODEL Hunting Percival P84 (1954)
 ENGINE 1 x BS "Viper 11",
10.9kN / 2450 lbf
 WEIGHTS
    Take-off weight 3310 kg 7297 lb
    Empty weight 2112 kg 4656 lb
 DIMENSIONS
    Wingspan 11.3 m 37 ft 1 in
    Length 9.9 m 33 ft 6 in
    Height 3.1 m 10 ft 2 in
    Wing area 19.9m 214.20 ft
 PERFORMANCE
    Max. speed 660 km/h 410 mph
    Range 1075 km 668 miles
 ARMAMENT 2 machine-guns (P84 Mk55)
 
SAAB J-21A SAAB J-21RB
 MODEL J-21 (1943)
 ENGINE 1 x Deimler-Benz DB 605B,
1100kW / 1475 hp
 WEIGHTS
    Take-off weight 4150 kg 9149 lb
    Empty weight 3250 kg 7165 lb
 DIMENSIONS
    Wingspan 11.6 m 38 ft 1 in
    Length 10.45 m 34 ft 3 in
    Height 3.96 m 13 ft 0 in
    Wing area 22.2m 238.96 sq ft
 PERFORMANCE
    Max. speed 640 km/h 398 mph
    Ceiling 11000 m 36100 ft
 ARMAMENT 1 x 20mm cannon,
4 x 13.2mm machine-guns
 MODEL J-21RB
 ENGINE 1 x DeHavilland "Goblin 3",
14.7kN / 3300 lbf
 WEIGHTS
    Take-off weight 4990 kg 11001 lb
    Empty weight 3200 kg 7055 lb
 DIMENSIONS
    Wingspan 11.6 m 38 ft 1 in
    Length 10.45 m 34 ft 3 in
    Height 2.95 m 10 ft 8 in
    Wing area 22.2m 238.96 sq ft
 PERFORMANCE
    Max. speed 800 km/h 497 mph
    Ceiling 12000 m 39350 ft
 ARMAMENT 1 x 20mm cannon,
4 x 13.2mm machine-guns
 
Vickers V610 Viking Vickers 618 Viking-Nene
 MODEL (1945) Vickers Viking IB
 ENGINE 2 x Bristol Hercules 634
1260kW / 1690 hp
 WEIGHTS
    Take-off weight 15354 kg 33850 lb
    Empty weight 10546 kg 23250 lb
 DIMENSIONS
    Wingspan 27.2 m 89 ft 3 in
    Length 19.86 m 65 ft 2 in
    Height 5.94 m 20 ft 6 in
    Wing area 81.94m 881.99 ft
 PERFORMANCE
    Speed Max - -
    Speed Cruise 338 km/h 210 mph
    Ceiling 7240 m 23750 ft
    Range w/max.payload 837 km 520 miles
 MODEL (1948) Vickers 618 Nene Vicking
 ENGINE 2 x Rolls-Royce Nene I
22.24kN / 5000 lbf
 WEIGHTS
    Take-off weight 15196 kg 33502 lb
    Empty weight 9548 kg 21050 lb
 DIMENSIONS
    Wingspan 27.2 m 89 ft 3 in
    Length 19.86 m 65 ft 2 in
    Height 5.94 m 20 ft 6 in
    Wing area 81.94m 881.99 ft
 PERFORMANCE
    Speed Max 753 km/h 468 mph
    Speed Cruise 632 km/h 393 mph
    Ceiling - -
    Range w/max.payload 555 km 345 miles
 
Vickers 630 Viscount Vickers 638 Viscount-Tay
Type 630 Viscount
 MODEL V630 Viscount
 ENGINE 4 x RR Dart 502
740kW / 990 hp
 WEIGHTS
    Take-off weight 18144 kg 40001 lb
    Empty weight 12746 kg 28100 lb
 DIMENSIONS
    Wingspan 27.13 m 89 ft 0 in
    Length 22.71 m 75 ft 6 in
    Height 8 m 26 ft 3 in
    Wing area 82.22m 885.01 ft
 PERFORMANCE
    Cruise speed 443 km/h 275 mph
    Ceiling 7620 m 25000 ft
    Range w/max.payload 2255 km 1400 miles
Vickers 663 Tay-Viscount
 MODEL V638 Viscount-Tay
 ENGINE 2 x RB44 Tay RTa1
27.8 kN / 6250 lbf
 WEIGHTS
    Take-off weight 18144 kg 40001 lb
    Empty weight 12746 kg 28100 lb
 DIMENSIONS
    Wingspan 27.13 m 89 ft 0 in
    Length 22.71 m 75 ft 6 in
    Height 8 m 26 ft 3 in
    Wing area 82.22m 885.01 ft
 PERFORMANCE    
    Cruise speed = =
    Ceiling = =
    Range w/max.payload = =